find the value of a and b

1 A causal LTI system has transfer function H(z)= with x(n) and y(n) as discrete time input 1-az-1 + bz-2 and output of the system respectively. If given y(0) = 1, X(1) = 2, (2) = 1, y(3) = 3, x(2) = 2, and x (3) = 1